backing-file: clean up the API

- Pass iocb to ctx->end_write() instead of file + pos

- Get rid of ctx->user_file, which is redundant most of the time

- Instead pass iocb to backing_file_splice_read and
backing_file_splice_write

Signed-off-by: Miklos Szeredi <[e-mail]>
Signed-off-by: Amir Goldstein <[e-mail]>

fs/backing-file.c

···
 	refcount_t ref;
 	struct kiocb *orig_iocb;
 	/* used for aio completion */
-	void (*end_write)(struct file *, loff_t, ssize_t);
+	void (*end_write)(struct kiocb *iocb, ssize_t);
 	struct work_struct work;
 	long res;
 };
···
 	struct kiocb *iocb = &aio->iocb;
 	struct kiocb *orig_iocb = aio->orig_iocb;
 
-	if (aio->end_write)
-		aio->end_write(orig_iocb->ki_filp, iocb->ki_pos, res);
-
 	orig_iocb->ki_pos = iocb->ki_pos;
+	if (aio->end_write)
+		aio->end_write(orig_iocb, res);
+
 	backing_aio_put(aio);
 }
 
···
 	revert_creds(old_cred);
 
 	if (ctx->accessed)
-		ctx->accessed(ctx->user_file);
+		ctx->accessed(iocb->ki_filp);
 
 	return ret;
 }
···
 	if (!iov_iter_count(iter))
 		return 0;
 
-	ret = file_remove_privs(ctx->user_file);
+	ret = file_remove_privs(iocb->ki_filp);
 	if (ret)
 		return ret;
 
···
 
 		ret = vfs_iter_write(file, iter, &iocb->ki_pos, rwf);
 		if (ctx->end_write)
-			ctx->end_write(ctx->user_file, iocb->ki_pos, ret);
+			ctx->end_write(iocb, ret);
 	} else {
 		struct backing_aio *aio;
 
···
 }
 EXPORT_SYMBOL_GPL(backing_file_write_iter);
 
-ssize_t backing_file_splice_read(struct file *in, loff_t *ppos,
+ssize_t backing_file_splice_read(struct file *in, struct kiocb *iocb,
 				 struct pipe_inode_info *pipe, size_t len,
 				 unsigned int flags,
 				 struct backing_file_ctx *ctx)
···
 		return -EIO;
 
 	old_cred = override_creds(ctx->cred);
-	ret = vfs_splice_read(in, ppos, pipe, len, flags);
+	ret = vfs_splice_read(in, &iocb->ki_pos, pipe, len, flags);
 	revert_creds(old_cred);
 
 	if (ctx->accessed)
-		ctx->accessed(ctx->user_file);
+		ctx->accessed(iocb->ki_filp);
 
 	return ret;
 }
 EXPORT_SYMBOL_GPL(backing_file_splice_read);
 
 ssize_t backing_file_splice_write(struct pipe_inode_info *pipe,
-				  struct file *out, loff_t *ppos, size_t len,
-				  unsigned int flags,
+				  struct file *out, struct kiocb *iocb,
+				  size_t len, unsigned int flags,
 				  struct backing_file_ctx *ctx)
 {
 	const struct cred *old_cred;
···
 	if (!out->f_op->splice_write)
 		return -EINVAL;
 
-	ret = file_remove_privs(ctx->user_file);
+	ret = file_remove_privs(iocb->ki_filp);
 	if (ret)
 		return ret;
 
 	old_cred = override_creds(ctx->cred);
 	file_start_write(out);
-	ret = out->f_op->splice_write(pipe, out, ppos, len, flags);
+	ret = out->f_op->splice_write(pipe, out, &iocb->ki_pos, len, flags);
 	file_end_write(out);
 	revert_creds(old_cred);
 
 	if (ctx->end_write)
-		ctx->end_write(ctx->user_file, ppos ? *ppos : 0, ret);
+		ctx->end_write(iocb, ret);
 
 	return ret;
 }
···
 	const struct cred *old_cred;
 	int ret;
 
-	if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)) ||
-	    WARN_ON_ONCE(ctx->user_file != vma->vm_file))
+	if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)))
 		return -EIO;
 
 	if (!file->f_op->mmap)
···
 	revert_creds(old_cred);
 
 	if (ctx->accessed)
-		ctx->accessed(ctx->user_file);
+		ctx->accessed(vma->vm_file);
 
 	return ret;
 }

fs/fuse/passthrough.c

···
 	fuse_invalidate_atime(inode);
 }
 
-static void fuse_passthrough_end_write(struct file *file, loff_t pos, ssize_t ret)
+static void fuse_passthrough_end_write(struct kiocb *iocb, ssize_t ret)
 {
-	struct inode *inode = file_inode(file);
+	struct inode *inode = file_inode(iocb->ki_filp);
 
-	fuse_write_update_attr(inode, pos, ret);
+	fuse_write_update_attr(inode, iocb->ki_pos, ret);
 }
 
 ssize_t fuse_passthrough_read_iter(struct kiocb *iocb, struct iov_iter *iter)
···
 	ssize_t ret;
 	struct backing_file_ctx ctx = {
 		.cred = ff->cred,
-		.user_file = file,
 		.accessed = fuse_file_accessed,
 	};
 
···
 	ssize_t ret;
 	struct backing_file_ctx ctx = {
 		.cred = ff->cred,
-		.user_file = file,
 		.end_write = fuse_passthrough_end_write,
 	};
 
···
 	struct file *backing_file = fuse_file_passthrough(ff);
 	struct backing_file_ctx ctx = {
 		.cred = ff->cred,
-		.user_file = in,
 		.accessed = fuse_file_accessed,
 	};
+	struct kiocb iocb;
+	ssize_t ret;
 
 	pr_debug("%s: backing_file=0x%p, pos=%lld, len=%zu, flags=0x%x\n", __func__,
-		 backing_file, ppos ? *ppos : 0, len, flags);
+		 backing_file, *ppos, len, flags);
 
-	return backing_file_splice_read(backing_file, ppos, pipe, len, flags,
-					&ctx);
+	init_sync_kiocb(&iocb, in);
+	iocb.ki_pos = *ppos;
+	ret = backing_file_splice_read(backing_file, &iocb, pipe, len, flags, &ctx);
+	*ppos = iocb.ki_pos;
+
+	return ret;
 }
 
 ssize_t fuse_passthrough_splice_write(struct pipe_inode_info *pipe,
···
 	ssize_t ret;
 	struct backing_file_ctx ctx = {
 		.cred = ff->cred,
-		.user_file = out,
 		.end_write = fuse_passthrough_end_write,
 	};
+	struct kiocb iocb;
 
 	pr_debug("%s: backing_file=0x%p, pos=%lld, len=%zu, flags=0x%x\n", __func__,
-		 backing_file, ppos ? *ppos : 0, len, flags);
+		 backing_file, *ppos, len, flags);
 
 	inode_lock(inode);
-	ret = backing_file_splice_write(pipe, backing_file, ppos, len, flags,
-					&ctx);
+	init_sync_kiocb(&iocb, out);
+	iocb.ki_pos = *ppos;
+	ret = backing_file_splice_write(pipe, backing_file, &iocb, len, flags, &ctx);
+	*ppos = iocb.ki_pos;
 	inode_unlock(inode);
 
 	return ret;
···
 	struct file *backing_file = fuse_file_passthrough(ff);
 	struct backing_file_ctx ctx = {
 		.cred = ff->cred,
-		.user_file = file,
 		.accessed = fuse_file_accessed,
 	};
 

fs/overlayfs/file.c

···
 	ovl_copyattr(file_inode(file));
 }
 
-static void ovl_file_end_write(struct file *file, loff_t pos, ssize_t ret)
+static void ovl_file_end_write(struct kiocb *iocb, ssize_t ret)
 {
-	ovl_file_modified(file);
+	ovl_file_modified(iocb->ki_filp);
 }
 
 static void ovl_file_accessed(struct file *file)
···
 	ssize_t ret;
 	struct backing_file_ctx ctx = {
 		.cred = ovl_creds(file_inode(file)->i_sb),
-		.user_file = file,
 		.accessed = ovl_file_accessed,
 	};
 
···
 	int ifl = iocb->ki_flags;
 	struct backing_file_ctx ctx = {
 		.cred = ovl_creds(inode->i_sb),
-		.user_file = file,
 		.end_write = ovl_file_end_write,
 	};
 
···
 	ssize_t ret;
 	struct backing_file_ctx ctx = {
 		.cred = ovl_creds(file_inode(in)->i_sb),
-		.user_file = in,
 		.accessed = ovl_file_accessed,
 	};
+	struct kiocb iocb;
 
 	ret = ovl_real_fdget(in, &real);
 	if (ret)
 		return ret;
 
-	ret = backing_file_splice_read(fd_file(real), ppos, pipe, len, flags, &ctx);
+	init_sync_kiocb(&iocb, in);
+	iocb.ki_pos = *ppos;
+	ret = backing_file_splice_read(fd_file(real), &iocb, pipe, len, flags, &ctx);
+	*ppos = iocb.ki_pos;
 	fdput(real);
 
 	return ret;
···
 	ssize_t ret;
 	struct backing_file_ctx ctx = {
 		.cred = ovl_creds(inode->i_sb),
-		.user_file = out,
 		.end_write = ovl_file_end_write,
 	};
+	struct kiocb iocb;
 
 	inode_lock(inode);
 	/* Update mode */
···
 	if (ret)
 		goto out_unlock;
 
-	ret = backing_file_splice_write(pipe, fd_file(real), ppos, len, flags, &ctx);
+	init_sync_kiocb(&iocb, out);
+	iocb.ki_pos = *ppos;
+	ret = backing_file_splice_write(pipe, fd_file(real), &iocb, len, flags, &ctx);
+	*ppos = iocb.ki_pos;
 	fdput(real);
+
 
 out_unlock:
 	inode_unlock(inode);
···
 	struct file *realfile = file->private_data;
 	struct backing_file_ctx ctx = {
 		.cred = ovl_creds(file_inode(file)->i_sb),
-		.user_file = file,
 		.accessed = ovl_file_accessed,
 	};
 

include/linux/backing-file.h

···
 
 struct backing_file_ctx {
 	const struct cred *cred;
-	struct file *user_file;
-	void (*accessed)(struct file *);
-	void (*end_write)(struct file *, loff_t, ssize_t);
+	void (*accessed)(struct file *file);
+	void (*end_write)(struct kiocb *iocb, ssize_t);
 };
 
 struct file *backing_file_open(const struct path *user_path, int flags,
···
 ssize_t backing_file_write_iter(struct file *file, struct iov_iter *iter,
 				struct kiocb *iocb, int flags,
 				struct backing_file_ctx *ctx);
-ssize_t backing_file_splice_read(struct file *in, loff_t *ppos,
+ssize_t backing_file_splice_read(struct file *in, struct kiocb *iocb,
 				 struct pipe_inode_info *pipe, size_t len,
 				 unsigned int flags,
 				 struct backing_file_ctx *ctx);
 ssize_t backing_file_splice_write(struct pipe_inode_info *pipe,
-				  struct file *out, loff_t *ppos, size_t len,
-				  unsigned int flags,
+				  struct file *out, struct kiocb *iocb,
+				  size_t len, unsigned int flags,
 				  struct backing_file_ctx *ctx);
 int backing_file_mmap(struct file *file, struct vm_area_struct *vma,
 		      struct backing_file_ctx *ctx);